'Cold fusion' explained

Your article on cold fusion (29 March, p 36) as well as the review of the book Undead Science: Science studies and the afterlife of cold fusion by Bart Simon (22 March, p 48), omit a simple and known explanation of the extra heat given off by metal hydrides such as palladium deuteride.

The extra energy comes from elastic relaxation. When hydrogen is forced into the metal, either by external pressure or by electrochemical means, the metal lattice swells to accommodate it. The new lattice is irregularly distorted and full of defects.

People who work with hydrides tell me that if you touch a block of palladium hydride, you will feel your hand grow warm. Apparently the readjustment of the solid structure goes on for months, and as the potential energy decreases, the liberated energy is radiated out as heat and conducted away.

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